Silencer



P 1937. H. H. MAXIM 2,093,893

SILENCER Filed Dec. 9, 1936 INVENTOR 157m flw/zm/r Mx/M Patented Sept. 21, I937 submerged to accomplished very l5 routine periodic inspection-and cleaning should danger of its location becoming known through the presence of exhaust noise.

quencies and a casing of the silencer proper.

In the present invention, low frequency attenuation? is obtained by using acoustic sidebranches, one or more of which may be used. In order to meet the requirement that the entire interior of the silencer be quickly and comnels, through which the exhaust multaneously. The channels are in parallel. ll One or the channels is positioned so as to extend so constructed without resorting to very large and cumbersome sidebranches. In the construction herein shown, the conductivities are not unduly large and sidepermit conduits distance from or inspection holes are be attenuated is,

branches are readily designed to meet the needs ofthe service.

Inasmuch as silencers suitable for use on submarines arewater-jacketed, the external vents are necessarily placed at the ends'of the silencer, rather than on the casing shell. The presence of .a water iaclset precludes the use of handholes placed in the shell of the silencer. Such cleanout therefore placed in the transverse. headers defining the acoustic sidebranches and are made large enough for a man to pass through, thus gaining access to the entire interior of the silencer.

For a further and better understanding of the invention, reference is now made to the drawing,-

in which,

Fig. 1 shows a longitudinal section in diagrammatic form of one embodiment of the invention; Fig.2 shows a section on line 2-.---? of Fig. 1; Fig. 3 shows another embodiment of the invention; and Fig. shows a section on line 4-4 of Fig. 3. Referring to Fig. l, the silencer comprises a cylindrical casing i, an end header 2 having a centrally disposed inlet connection 3, and a header 4 having an eccentrically disposed connection 5. The interior of the'casing i is divided longitudinally into five compartments by transverse headers 6, l, 8 and 9. Each of these headera is provided with two openings, each tangent at its outer edge to the casing l and centered on the vertical diameter of the circular header, to

it and ii to extend longitudinally from the header 6 to the header 9. Each of these conduits H], H is furnished with slotlike peripheral openings at points intermediate each adjacent pair of transverse headers, whereby both of said channels are acoustically coupled into their corresponding sidebranches. The slotlike openings are positioned in an identical manner in each of the conduits lg, H so that any given sidebranch volume is acoustically the same the inlet end of said conduits as measured along either channel. This assures the proper phase relations being maintained. Otherwise it would be possible for sound waves to enter the sidebranch chambers from one main conduit and leave through the other, thus interfering to some extent with the proper action of the device. The main channel iii has, for instance, a conductivity or inertance formed by the slot l2 and the main channel ii, a conductivity formed by the slot 13, each simultaneously opening into the closed chamber l4 formed by the casing I, the transverse partitions B, l, and the outer surfaces of those portions of said conduits which lie between said headers. In other words, the volume or capacitance of the resonator sidebranch is that of a cylinder less the volume taken up by the two main channels passing there- .through. The resonant frequencies of this side- Similarly, the conductivities It, Is and the volume l1 form another resonator disposed in shunt to the main channels, while the conductivities l8, I9, together with the volume 20 form a third sidebranch. The longitudinal spacing of the various headers determines the relative volumes of the various sidebranches. Thesemay be all the same or all different. Since the designer of the silencer generally knows in advance, through measurements in the field, what the frequency range to it is readily possible to design the low frequency traps so that ample coverage header 2 and the partition For instance, the with the man hole will be obtained. The space 2i, formed between the header tend the partition 5, serves as a combining chamber for the two main channels it, it, whereby the exhaust gases are directed out through the eccentric outlet connection 5. It is found that this eccentric opening snot only permits quick draining of the interior of the silencer but, by making the acoustic paths to the entrance of the two main channels of slightly difierent lengths, serves to increase the attenuation ofiered by the silencer as a whole through introducing reflection losses in the space M. The chamber 22, formed within the casing i and between the t3 serves as an inlet main channels and, in this either the high frequency diagrammatically as 23 or a chamber for the two embodiment, houses silencing unit shown suitable evaporator.

The interiors of the chambers It, H, and 20 are made accessible for inspection and cleaning by means of man holes'having suitable cover plates. transverse partition 9 is fitted 2t and itscorresponding cover plate 25. Similar man holes are provided in the partitions I, 8 whereby the interiors of the chambers it, H are readily accessible. The inlet header 2 is made removable so that the evaporator or high frequency silencing unit may be withdrawn, thus exposing the man hole cover plate 25, which may then be removed. Gas vents 26, 2'! are provided at the upper edges of the and headers 2, 5 respectively.

Fig. 3 shows a construction similar to that of Fig. 1 with a modification in the man hole design. In the case of silencers for the auxiliary engines of the submarine, the device may be so small as to ,preclude the possibility of there being space enough for a man to pass through a cleanout hole. In this case, hand holes are provided. This limits the number of closed sidebranches of this type to two, since the hand holes must be placed in the outer headers defining the lowfrequency'silencing unit. A high frequency silencing unit is shown at-' tached to the inlet head. The silencer comprises the casing 28, the transverse headers 29, 30, 3i and a similar arrangement of main channels and volumetric sidebranches. Sidebranch 32 is accessible through hand hole 33 and sidebranch 34 is accessible through hand hole 35. Both end headers 36, 37 are removable. The inlet header 36 is fitted with a centrally disposed inlet opening 38 and supports a high frequency unit 39, which may be of any conventionalconstruction, while the outlet header 31 has an eccentric outlet opening 40.

In the embodiment shown, the water jacket is omitted for purposes of clarity.

I claim:

1. An acoustic silencing device comprising a pair of main sound conducting channels, means for coupling said channels in parallel to a source of sound waves, and a closed acoustic sidebranch substantially surrounding both of said channels and acoustically coupled to each of them.

2. An acoustic silencing device comprising a pair of main sound conducting channels, means for coupling said channels in parallel to a source of sound waves, and a closed acoustic sidebranch substantially surrounding both of said channels and acoustically coupled to each of them through peripheral slots in the channels.

3. A device of the class described comprising a member defining a cylindrical cavity and a pair of conduits passing therethrough in a direction substantially the closed except for parallel to the axis thereof, said conduits being formed with openings whereby said cavity is acoustically coupled to each of said conduits.

4. A silencer comprising a pair of substantially horizontally disposed main sound conducting channels arranged one above the other in a substantially vertical plane acoustic sidebranches each acoustically coupled to each of said channels at points along its length.

5. An acoustic silencing device comprising a pair of sound conducting channels, and an acoustic sidebranch coupled to both of said channels by conductivities having substantially equal acoustic paths thereto from the sound-receiving ends of said channels.

6. An acoustic silencing device comprising a pair of substantially straight sound and gas conducting channels extending horizontally and arranged one above the other in a vertical plane, and an acoustic sidebranch coupled to both of said channels and closed except for said coupling, entire volume of the sidebranch being above the bottom of the lower channel and below the top of said upper channel.

7. An acoustic silencing device comprising a pair of main sound conducting channels, means for coupling said channels in parallel to a source of sound waves, and an acoustic sidebranch acoustically coupled to both of said channels at points where said sound waves in the respective phase one with another and said coupling.

8. A silencer comprising a generally cylindrical casing, a plurality of longitudinally spaced transverse partitions dividing said casing into a plurality oi longitudinally spaced cylindrical compartments, and a pair of gas and sound conducting channels connected in parallel and pass ing through said casing and partitions and each acoustically coupled to each of said cylindrical compartments.

9. A sliencer comprising an inlet chamber, an outlet chamber, a pair of substantially straight sound and gas conducting channels connected in parallel between said chambers, and at least 10. A silencer in accordance with claim 9 in which the channels have their axes horizontally disposed and lying in a common vertical plane.

11. A silencer in which the slots in the several channels are identically spaced along the lengths thereof.

12. A silencer for internal combustion engines comprising a generally cylindrical casing, a plurality of transverse headers therein dividing the easing into a plurality of cylindrical compartments, an inlet chamber at one end oi the easing, an outlet chamber at the other end of the casing, sound and of said inlet and outlet chambers respectively, a. pair of substantially straight main sound and gas conducting channels ,in parallel extending from said inlet chamber to said outlet chamber, said channels being disposed horizontally in the same eral slots in the channels,

substantially horizontally arranged accordance with claim 9 in gas connections into and outvertical plane and each being substantially tangent to the inner surface of said casing, and'a plurality of acoustic sidebranches disposed within said cylindrical compartments, coupled acoustically to each of the main channels by periphand closed except for said coupling, said slots in the several channels being identically spaced along the lengths thereof.

13. A silencer for both high and low frequencies comprising a casing, at least one main sound and gas conducting channel passing through the casing, a plurality of transverse headers within the casing forming between them a plurality of acoustic sidebranches acoustically coupled to said channel but closed except for said coupling, a removable high frequency silencing unit positioned within one end of the casing, holes in the transverse headers to permit access to the interior of the closed acoustic sidebranches when the high frequency silencing unit has been removed.

14. In a device of the class described, a cylindrical casing defining a cavity, and a pair of conduits passing through said cavity in a direction parallel to the axis thereof, said conduits being acoustically coupled to said cavity at points such that sound waves emanating from a common source and traveling through said conduits are substantially in phase.

15. A silencer comprising a pair of main gas and sound conducting channels of substantially equal length, means for coupling said channels in parallel to a common source of sound, a plurality of acoustic sidebranches disposed in shunt to both 01' said channels along the lengths thereoi and each acoustically coupled to each of said channels the spacing and formation of said couplings between the channels and the sidebranches being substantially identical in each of the channels, whereby certain groups of sound frequencies traveling in phase simultaneously through said channels are highly attenuated by said sidebranches.

16. A silencing device comprising a pair of spaced main sound conducting channels, an acoustic sidebranch coupled to one of said channels by an opening at the top thereof and to the other of said channels by an opening at the bottom thereof, and means for connecting said channels in parallel for the conduction of sound simultaneously therethrough.

17. A silencing device comprising a pair of sound and gas conducting channels arranged one above the other, and at least one acoustic sidebranch interposed between the two channels and acoustically coupled to both of them through openings therein, the relative positions of the channels, the sidebranch, and the openings being such that water may enter said sidebranch through the opening therefrom into the lower main channel and completely fill the interior volume of said sidebranch, the imprisoned gas or air passing out through the conductivity in said upper channel so that both the channels and the sidebranch can be quickly and completely filled with or emptied or water.

HIRAM HAMILTON MAlUM.

and closed except for such coupling, 

